The spinal column generally comprises thirty three vertebrae whose ends articulate by interposed pads of discs or cartilaginous tissue. On occasion, such discs are replaced by bone grafts which, in time, fuse to the ends of adjoining vertebrae.
Known spinal fixation implants may include generally parallel elongate members and associated transverse connectors. See, e.g., U.S. Pat. Nos. 5,522,816 and 5,688,272. Spinal implant systems which comprise longitudinal members composed of a chain of interconnected links which may be cross-connected at a distal end are described in U.S. Pat. No. 5,716,357. The links may be in the form of plates or rods with a central portion and end portions apertured for attachment to vertebrae by bone bolts or like means. The apertured end portions may be offset from the central portion such that a portion of the graft area is exposed upon implantation. The exposed graft area provides greater surgeon accessibility to the bone graft site and optimization of the graft bed and of useful graft volume.
There is a need for means and a method to immobilize or anchor bone grafts in proper position on exposed anterior portions of a vertebra or vertebrae as fusion proceeds.